It is known, for example, from U.S. Pat. Nos. 4,935,820 and 5,050,001 to utilize a single crystal display to produce a color image on a photographic material. The LCD uses digital information obtained from scanning the negative or from any other source. The problem associated with the implementation of an LCD array for printing onto a photographic material is that light uniformity across the LCD varies across the device. In addition, uniformity of the LCD device can vary over time and temperature. The '820 patent suggests that corrections in luminations may be carried out by individual adjustment of the pixels of the LCD. A disadvantage of such an approach is that the dynamic range of the digital data of the LCD is reduced. An additional problem is that lower quality prints are produced due to the limited dynamic range of a single LCD.
The present invention provides a method and apparatus for digital printing onto photographic media which corrects for light non-uniformity of the exposure light. This, is accomplished by providing a second LCD in line with the imaging AMLCD and utilizing a calibration procedure for determining corrective values used to correct the non-uniformity.